Tektronix
leads the market in developing products for new and emerging audio,
video, and cable technologies. This time in the field of MPEG-2 transport
streams. The MTS100 is an innovative solution to the problem of testing
equipment used in a MPEG-2 network.

Perform creation, generation
acquisition, and analysis of MPEG-2 transport streams quickly using
the intuitive icon-driven user interface. The MTS100 can create, generate,
acquire, and analyze MPEG-2 transport streams. From a transport stream
as basic as a single program to a more complex transport stream with
multiple programs and many elements in each program, the MTS100 can
handle it.

All applications are preloaded, making the MTS100
fully configured and ready to use immediately. Each of the six specific
software applications performs their own function to aid in evaluating
your system.

The MTS100 gives you the ability to create transport
streams with complete control over many of the various MPEG-2 parameters.
A few examples are: placement of time stamps, timing offsets, data
rates, PES packet size, jitter, channel coding, and DVB-SI information.

An included CD-ROM contains several audio and video elementary
streams. The video elementary streams contain both motion sequences
and traditional television test patterns. Use these elementary streams
for creating your own MPEG-2 transport streams.

Analyze acquired
transport streams using a simple graphical interface. The hierarchical
view gives an outline of the transport stream's structure, while the
interpreted view lets you examine syntax and the data values for each
field in the packet headers. It will even allow you to examine the
actual hex and binary values. It searches for errors in the transport
stream, PES packet, and Table Headers, highlighting any it finds.

The Analyzer application has easily accessible, clear explanations
of the fields and parameters. You could even use the Analyzer to train
people on the composition of the MPEG-2 transport stream.

Data
rates from 1 Mbps to 45 Mbps are available. With the 8 GB of storage
capacity, this allows a minimum of 20 minutes of acquisition or generation
time (four files, 5 minutes in length at 45 Mbps). The acquisition
or generation can be made nearly continuous by using the end-to-start
looping feature.

The MTS100 operates on a Windows NT™ platform.
This makes interconnecting to any existing network relatively simple.

Analyzer Features

Multiple document windows

Hierarchical transport-stream view

Packet header displays

Syntax and semantic information

Timing analysis (PCR
and PTS/DTS)

Error analysis of the Packet Header

Extract elements for use in other transport streams

Multiplexer Features

Interactive configuration definition

Hierarchical and dynamic views

Configuration stored
as ASCII file

Many variable parameters

PSI
and SI Table Editor Features

Edits nearly all ETS 300
468 October 1995 parameters

Checks both inter- and intra-table
coherence

Global view displays table interrelationships

Channel Coding/Decoding Features

Meets DVB
baseline system requirements for satellite broadcasting

Packet Jitter Features

Jitter all or only selected
program PIDs

Four jitter types available

Jitter
amplitude and frequency are user definable

Data Store
Features

Controls the I/O

Manages the Data
Store Disks for maximum efficiency

Interfaces

The MTS100 provides several interfaces for transmitting and receiving
the transport streams. (SMB to BNC adapter cables are also provided.)

G703 Ports

This serial interface complies with the electrical
characteristics of ITU-T rec. G703 (HDB3 code) for 8.448 and 34.368 Mbps.
These are the only G703 frequencies available. The mechanical connectors
are SMBs.

ECL Serial and Parallel Ports

The ECL Serial
and ECL Parallel ports share the same 25-pin subminiature D connector.
The parallel version provides eight balanced data pairs while the
serial version provides one. Additionally, CLOCK, DATA_VALID, and
header-sync (PSYNC) values are available. The voltages are at ECL
levels. The maximum operating bit rate is 45 Mbps and the minimum
is 1 Mbps.

A control port is available to regulate the flow
of data in this port. The control port is a subminiature 9-pin D connector,
and adds flexibility to the ECL Parallel and Serial port by adding
three control signals that provide two more operating modes.

TTL 50 Ohm

The TTL 50 ohm serial interface takes the form
of a clock and data signal. The signals operate at TTL levels, with
a maximum data rate of 45 Mbps. The connectors are male SMBs (one
data and one clock). This port can be synchronized to an external
clock using the Clock Port.

10 Mb Serial Port and Clock (RS-422
Levels)

This serial interface provides a differential signal
at RS-422 levels. It provides both input and output ports. The mechanical
connector is a 9-pin subminiature D connector.

Clock Port

This input provides timing for the TTL 50 ohm and 10-Mb Serial
ports. It expects inputs at TTL levels. The maximum operating frequency
is 45 MHz. The mechanical connector is an SMB male.

Analyzer

There is a tremendous amount of information in a transport stream.
The Analyzer displays this information in a logical and convenient
manner. Figure 1 gives the hierarchical tree display shown when first
performing an analysis. From here, you can quickly see an overview
of the transport stream.

Figure 1. The Analyzer's
hierarchical view.

The hierarchical view contains:

The transport stream (TS)

The PSI tables (PAT,
NIT, and PMT)

The PES packets

The elementary streams
(video, audio, or data)

You can shift to a more detailed
view, the interpreted view shown in Figure 2. This view gives the
details of all Packet Headers, including PAT, PMT, NIT, PES, transport,
and DVB-specific tables.

Figure 2. The Analyzer's
interpreted view.

There are two parts to each
parameter in this display: syntax and semantic. The syntax defines
each field, while the semantic gives the current value (in decimal
or hexadecimal). Obtain more information on either field by double-clicking
on it. (Figure 2 shows the additional information available when the
syntax portion of the PID is double-clicked.) If the syntax information
is not required, a binary- or hex-dump view is also available.

Scrolling through the packets is easy. Use the Next or Previous
arrow button at the bottom of the application window. You can also
specify a packet by the number.

Each packet and table have
a defined structure and the Analyzer allows you to view each of these
to check structure and search for errors. Parameters in red, flag
errors.

The Analyzer performs error analysis. The application
calculates the table CRCs and compares them to the CRC value in the
table data. The semantic values are compared to the MPEG-2 transport
stream standard. Any value in error is flagged in red. The Analyzer
searches for errors in the interpreted view and automatically displays
the first one it finds. An explanation of the error is available when
the semantic value is double-clicked.

A graphical display,
as shown in Figure 3, is used to express the timing. All the relevant
information about the PCR is available by double-clicking on the clock
icon. You can also display the PCRs in a table format listing the
parameters for all the PCRs in the selected display.

Figure 3. The PCR display.

The placement
of the PTS and DTS in the packet headers (Figure 4) has its own graphical
interface. It gives the placement of the PTS, DTS, and access unit
arrival times. The video access unit content type (I, P, or B frame)
can be determined from this display. If you prefer, display the PTS/DTS
in a table format listing the values of the parameters.

Figure 4. The PTS/DTS display.

Display
the percentage of the multiplex rate each PID is using in a pie chart,
using the Multiplex Allocation command. This feature is useful to
view all PIDs in the system and how much time is being used by each
one.

The Analyzer can extract portions of a transport stream
and save it to a file for further evaluation or reuse. The following
parts of a transport stream are available for extraction:

Transport packet/payloads (all or only a specific PID)

Tables (view them using the PSI and SI Table Editor application)

PES packets (all or only a specific stream type)

Individual
elementary streams

Multiple windows are available in
the Analyzer application. You can display the hierarchical view, interpreted
views, and timing displays simultaneously.

Multiplexer

The Multiplexer application allows you to generate transport
streams to rigorously test your own equipment. This guarantees a "good"
signal as the starting point for any system test.

The Multiplexer
can create transport streams with up to 20 programs. Each program
can have a maximum of 10 elementary streams, with a maximum of 5 of
any one elementary stream type.

Figure 5 shows the hierarchic
view of the Multiplexer. This view allows you to see the structure
of the multiplex while you are creating it.

Figure 5. The
hierarchic display.

The standard structure
contains the PSI (Program Specific Information) configuration including:
the PAT (Program Association Table), PMT (Program Map Table), NIT
(Network Information Table), and the Programs with their elementary
streams. There is also a DVB configuration (Figure 6) that includes
additional information for digital broadcasting in Europe. The SI
(System Information) includes: NIT (moved from the PSI), BAT (Bouquet
Association Table), SDT (Service Description Table), and EIT (Event
Information Table). (These tables can use their default values, or
customize them using the PSI and SI Table Editor application.)

Figure 6. The hierarchic display with DVB tables.

As you fill the multiplex, the bar graph on the left
keeps you abreast of the amount of data rate left in the multiplex.
It displays the highest usage rate.

The dynamic display (Figure
7) gives insight into the timing relationships between the programs
in the multiplex. It allows you to see the start and stop times for
each program and the data rate all programs contribute to the multiplex
at a selected time.

Figure 7. The dynamic
display.

The Multiplexer does not create the
transport stream as you add and adjust the parameters, rather it makes
a configuration file. This speeds up the application and allows you
to create slight variations to the transport stream easily. Before
creating the transport stream, the program checks for errors and allows
you to correct any it finds. The Multiplexer generates the transport
stream on either the system disk or the Data Store Disks. While it
generates the transport stream, the Multiplexer gives information
about the estimated final system clock time and the running time.

Within the Multiplexer application the following parameters are
user adjustable:

Multiplex Rate of the transport stream

Global start time of the transport stream (system clock value)

PSI insertion period

NIT insertion period

PAT values for the program PIDs

PMT information (using the
PSI and SI Table Editor application)

The PCR period for a
program

The program start time (relative to system clock)

ES rate

PES size

DTS offset (for a video elementary
stream)

PTS offset (for an audio elementary stream)

The following parameters are displayed, although they are not
user adjustable:

PSI and SI Table Editor

DVB-specific (Digital
Video Broadcasting) tables add information enabling DVB IRDs (Digital
Video Broadcasting Integrated Receiver Decoders) to automatically
tune to a particular service and allows grouping of services into
categories with relevant schedule information. These tables provide
the EPG (Electronic Program Guide) information. Data necessary for
the DVB IRD to automatically configure itself is available in the
NIT, SDT, BAT, and EIT tables.

Figure 8. The PSI/SI
Table Editor.

The PSI and SI Table Editor allows
the user to change the data in the SI and PSI tables to fit their
requirements. Table 1 gives the parameter types available for each
of the table types.

Table 1 – The parameters available
for each table

Table

Parameters available

PMT

Elementary streams, descriptor, or subdescriptor

NIT

Transport streams, descriptor, or subdescriptor

SDT

Service, descriptor, or subdescriptor

BAT

Transport stream, descriptor, or subdescriptor

EIT

Event, descriptor, or subdescriptor

Nearly all the parameters described in ETS 300 468
October 1995 are editable in this application.

Global View
(Figure 9) from this application shows the interrelationship between
selected NIT, SDT, and EIT files. These files can have some interrelationship
or none at all. (The illustration shows files with a high amount of
interrelationships.) The association between the files is explained
below:

NIT contains the transport streams.

Transport
streams define transport stream ID.

SDT must have the same
transport stream ID.

SDT contains services.

Services
contain service descriptors and service IDs.

EIT must have
the same service ID and transport stream ID to be interrelated to
the SDT and NIT.

Figure 9. The global
view showing the association between the tables.

The PSI and SI Table Editor provides a coherence check of all
open tables. It checks both the inter- and intra-table parameters
for coherence to the standard.

Channel Coding/Decoding

The European Digital Broadcasting Project (DVB) has specified
a baseline system for satellite broadcasting. The channel coding portion
of the specification has the following coding flow:

Energy
dispersal (randomizing) (If not used, it is replaced by a "B8" sync
byte coding scheme.)

Reed-Solomon Code RS (204, 188) (can
be customized)

Convolutional interleaver

Viterbi
Code (1/2, 2/3, 3/4, or 7/8)

The decoding flow is:

De-interleaving

Reed-Solomon decoding and error
correction

Energy dispersal removal

This application
allows you to chain the coding or decoding together to meet the DVB
coding requirements or break the chain to test your own coder or decoder.

Packet Jitter

To aid in the design and evaluation of
the decoder PLL, knowledge of the specific amount of jitter introduced
into a system is mandatory. This jitter would represent the time variance
of the transmission system. The Packet Jitter application accomplishes
this by modulating the PCR data away from the correct values. The
modulation can take the form of a sine wave, square wave, step, or
random variations. Define the period and amplitude of the jitter to
meet your own requirements.

Transport streams created with
this application allow for real-time tests of the decoder. The receiver
PLL is stressed as it tries to filter out these variations to produce
a stable reference clock.

Data Store Manager

The Data
Store Manager application controls the real-time generation and acquisition
of the transport streams. It determines which of the ports are active
at any given time and all the variables (bit rate, control signals,
and clocks).

This application also manages file storage on
the Data Store Disks. It performs general housekeeping functions such
as moving files, deleting files, and managing the disk space on the
Data Store Disks.